ARS | Publication request: Porous rice powder from the precipitation of gelatinized flour or starch paste with ethanol

Submitted to: Starch/Starke
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 14, 2012
Publication Date: March 7, 2013
Citation: Patindol, J.A., Shih, F.F., Ingber, B.F., Champagne, E.T., Boue, S.M. 2013. Porous rice powder from the precipitation of gelatinized flour or starch paste with ethanol. Starch/Starke. 65:296-303.

Interpretive Summary: Pregelatinized starch (also called pregels or instant starch) is a valuable material for food, pharmaceutical, and other industrial applications. Its manufacture generally involves cooking the raw starch (gelatinization), and then recovering it as a dry powder. In this work, an alternative procedure of recovering the dry powder is employed, i.e., through precipitation with ethanol. Hot paste obtained by autoclaving a 5-7% rice flour or starch slurry was precipitated with ethanol (three extractions) to produce a dry, porous, pregelatinized powder. The flour and starch-derived powder had an average particle size of 75.0 and 41.6 micrometers, respectively. In comparison with native flour and starch, the bulk density of the pregelatinized powders decreased; solvent uptake (water, oil, and alcohol), swelling power, and in vitro starch digestibility increased; whereas, gel consistency, freeze-thaw stability, and apparent amylose content sparingly changed. Changes in morphological and physicochemical properties were generally more evident on the starch-derived products compared with the flour-derived counterparts. The extent of the changes was also affected by severity of the gelatinization treatment. The pregelatinized rice products as developed, may be suitable for food and non-food end-use.

Technical Abstract: Hot paste obtained by autoclaving (130oC, 20 psi, 20-30 min) a 5-7% (w/w) rice flour or starch slurry was precipitated with ethanol (three extractions) to produce a dry, porous, pregelatinized powder with an average particle size of 75.0µm (flour-derived powder), and 41.6µm (starch-derived powder). The microstructure of the individual particles was characterized by an interconnecting lattice of irregularly-shaped vesicles, and with cavities of varying size and shape. The vesicular network was thinner and finer for the starch-derived products, compared with the flour-derived ones. In comparison with native flour and starch, the bulk density of the pregelatinized powders decreased; solvent uptake (water, oil, and alcohol), swelling power, and in vitro starch digestibility increased; whereas, gel consistency, freeze-thaw stability, and apparent amylose content sparingly changed. Changes in morphological and physicochemical properties were generally more evident on the starch-derived products compared with the flour-derived counterparts. The extent of the changes was also affected by severity of the gelatinization treatment (varying slurry concentration and autoclaving duration). The pregelatinized rice products as developed, may be useful in food and non-food applications.